1. Field of the Invention
I have found a new improved concentrated colonic purgative formulation made by combining inorganic salts and polyethylene glycol (PEG) in a small volume of water. This formulation is effective to produce colonic purging to prepare the colon for surgical or diagnostic procedures and surprisingly does not cause clinically significant changes in electrolyte balance.
2. Background Information
In sigmoidoscopy, colonoscopy, radiographic examination, preparation for patients undergoing bowel surgery, and other medical or diagnostic procedures on the colon, it is important that the colon be thoroughly purged and cleaned. In particular, it is essential that as much fecal matter as possible be removed from the colon to permit adequate visualization of the intestinal mucosa. This is important prior to, for example, diagnositc procedures such as flexible sigmoidoscopy or colonoscopy, diagnostic examinations widely performed to screen patients for diseases of the colon. In addition, it is important that the intestines be cleansed thoroughly in order to obtain satisfactory radiographs of the colon. The same condition also applies when the colon is preoperatively prepared for surgery, where removal of fecal waste materials is critically important for patient safety.
Large volume orally administered compositions have been developed for use as gastrointestinal washes for diagnostic purposes or for use as cathartic laxatives. Such orally administered preparations are usually formulated as dilute or isotonic solutions of electrolytes such as sodium sulfate, sodium bicarbonate, sodium chloride and potassium chloride. These orally administered compositions are useful in the rapid cleansing of the colon for diagnostic purposes. These formulations may include other agents such as polyethylene glycol. These formulations have generally been administered in a quantity of about four liters as isotonic solutions. One example composition is GoLYTELY® formulated according to the following: polyethylene glycol 59 g, sodium sulfate 5.68 g, sodium bicarbonate 1.69 g, sodium chloride 1.46 g, potassium chloride 0.745 g and water to make up one liter (Davis et al. Gastroenterology 1980;78:991-995).
Commercially available products embodying these formulations sometimes utilize polyethylene glycol, a non-absorbable osmotic agent, with an isotonic mixture of electrolytes for replenishment, so that patients do not become dehydrated or experience clinically significant electrolyte shifts. Because the solutions are isotonic, patients are required to ingest a significant amount of volume of these solutions, up to one eight ounce glass every ten minutes for a total of one gallon of fluid, to achieve effective purging
Sodium sulfate and phosphate salts have been used as laxatives when diluted in a small volume (˜300 mL) concentrated solution and taken in tablespoon sized (15 ml) daily doses. An example of this use is Glauber's Salt's (containing sodium sulfate). However, because of their small volumes, when used in this fashion they do not sufficiently clean the colon for diagnostic or surgical procedures. Also these small volume preparations do not contain polyethylene glycol. Sodium sulfate combined with polyethylene glycol and various other salts, administered in large volumes (1 gallon) over a short period of time is an effective gastrointestinal lavage, which cleanses the colon prior to colonoscopy or surgical procedures as described above.
The large volume required for effective use of this type of formulation for lavage is frequently associated with distention, nausea, vomiting and significant patient discomfort. Thus, while these formulations are generally effective, they are not well tolerated.
Another drawback of these prior art preparations is their unpleasant, bitter, saline taste. This can promote nausea and vomiting in sensitive patients—thereby preventing ingestion. It is difficult to overcome this unpleasant taste, even the most common natural sweeteners such as glucose, fructose, saccharose, and sorbitol could change the osmolarity of these orally administered solutions resulting in potentially dangerous electrolyte imbalances.
In an attempt to avoid the problems associated with the high volume types of preparations, other investigators have utilized ingestible preparations which consist of aqueous solutions of concentrated phosphate salts. The aqueous phosphate salt concentrate produces a tremendous osmotic effect on the intra-luminal contents of the bowel and therefore, evacuation of the bowel occurs with a large influx of water and electrolytes into the colon from the body. These phosphate salt preparations have been developed for the purpose of decreasing the volume required in colonic purgations. One such preparation basically is comprised of 480 grams per liter monobasic sodium phosphate and 180 grams per liter dibasic sodium phosphate in stabilized buffered aqueous solution and is sold under the brand name Fleets Phospho-Soda.™. Patients are typically required to take two (2) three ounce doses of this preparation, separated by a three to 12 hour interval for a total of six ounces (180 ml), which is a significant reduction compared to the large 1 gallon volumes required by the high volume preparations. Additionally, non-aqueous tablet or capsule formulations of sodium phosphates and sulfates have been used (U.S. Pat. Nos. 5,997,906, 6,162,464, and 5,616,346).
These small volume sulfate/phosphate solutions and non-aqueous formulations have been shown to cause massive electrolyte and fluid shifts that are clinically significant to the patient (US Food and Drug Administration, Center for Drug Evaluation and Research, Sep. 17, 2001; 2002 Physician's Desk Reference, prescribing information for Fleet's Phospho Soda and InKine Pharmaceutical's Visicol®). The terms “clinically significant” as used herein are meant to convey alterations in blood chemistry that are outside the normal upper or lower limits of their normal range or other untoward effects. These solutions are hyperosmotic; that is the electrolyte concentration of the solution is much higher than the electrolyte concentration in the human body. Available products, as Fleet's Phospho-Soda, and the solid dosage form such as Visicol tablets (sodium phosphate salts) are examples of small volume electrolyte preparations. All of these products have been seen to cause clinically significant electrolyte disturbances and fluid shifts, and disturbances in cardiac and renal function when administered to patients (US Food and Drug Administration, Center for Drug Evaluation and Research, Sep. 17, 2001).
To overcome the risks and electrolyte disturbances that occur with the small volume laxative preparations, large volume “lavage” solutions were developed to be isotonic. Preparing a patient for a surgical or diagnostic procedure on the colon with such an isotonic lavage would result in only minimal fluid and electrolyte shifts in the patient. GoLytely®, NuLytely®, and CoLyte® are examples of such large volume ravages. Because these lavages are isotonic, the patient experiences minimal, non-clinically significant fluid and electrolyte shifts, if any, upon their administration.
From the foregoing, it can be seen that the two approaches to colonic lavage have significant drawbacks that have not been resolved by prior attempts. The isotonic solutions, while not causing clinically significant fluid or electrolyte shifts, are, of necessity, of large volume, and difficult for patient ingestion. The hypertonic solutions or concentrated non-aqueous formulations are sometimes inadequate to prepare the colon and more importantly, can cause clinically significant electrolyte and fluid shifts, which have been known to cause deaths. Thus, it is desirable to have a small volume orally administered colonic purgative formulation which may be easily and conveniently administered and which avoids the clinically significant problems and objectionable tastes of known formulations. It can also be seen that it is desirable to have such a purgative formulation which may be administered without the large volumes necessary in conventional formulations and which avoids other potentially irritant chemicals or chemicals which could effect osmolality. In the nearly 20 years since the advent of large volume colonic lavage solutions, there has not been success in discovering an effective small volume gastrointestinal cleansing preparation that minimized fluid or electrolyte shifts. Concentrating the large volume lavages into smaller volumes does not achieve the same effectiveness, and is not as safe. This is because the components are not soluble in the small volumes necessary and because the concentrations are such that dangerous electrolyte shifts could occur. One purpose of the present research was to develop a safe, effective, and well tolerated small volume solution made up of a high concentration of poorly absorbable salts that induce a colon cleansing catharsis after oral ingestion without clinically significant alternation of sodium, chloride, bicarbonate, potassium, calcium, and phosphate level and balance or other untoward effects on the recipient.